This invention relates in general to opposed antifriction bearings and, more particularly, to an apparatus or an installation method for setting antifriction bearings between a housing and a differential carrier or case or a gear reduction unit constructed of dissimilar materials or metals.
Differential gear mechanisms transfer rotational torque from an input shaft member to a pair of output shaft members. One typical application of a differential gear mechanism is that of an automobile with the pair of output shaft members having the rear wheels attached thereto. A torque generating device such as a gasoline engine or an electric motor is typically used to drive the input member. The torque from the torque generating device is transferred to the input shaft member of a differential gear mechanism by a yoke that is splined to engage with one end of the input shaft member. In a conventional differential gear assembly the output shaft members are generally positioned perpendicular to the input shaft member. Most differential gear mechanisms use a drive pinion gear that mates with an adjoining ring gear to transfer the torque from the input shaft member to the output shaft members. Antifriction bearings are incorporated into the differential gear assembly to allow all of the shaft members to rotate in a generally free manner. An example of an antifriction bearing is a tapered roller bearing. The tapered roller bearing includes a cone having an inner race, a cup having an outer race, and a plurality of roller elements contained within a roller cage positioned between the inner and outer races.
Some components that are found in a differential gear mechanism may include a housing that is used to enclose the mechanism and a differential carrier or case. In some differential gear mechanisms the housing is constructed of a lightweight material such as aluminum that has a high coefficient of thermal expansion. The differential carrier or case is constructed of iron, steel, or another metal that has higher strength than the housing and a lower coefficient of thermal expansion than aluminum. Due to the differences in the materials or metals used, thermal expansion between the iron differential carrier and the aluminum housing may occur. If thermal expansion occurs when the apices of the antifriction bearings are facing outward, then the housing will expand axially to a greater amount than the differential carrier causing the bearings to loosen. Additionally, the diameter growth of the housing bores containing the bearings will expand to a greater amount causing even more loosening of the bearings. If this occurs then the antifriction bearings found in the differential gear mechanism may become loose which can cause the mechanism to rotate improperly, wear unevenly or prematurely, fail, or produce noise.
In a typical automotive hypoid axle the antifriction bearings in the form of tapered roller differential bearings are installed with their apices facing outwardly. In an effort to compensate for the differences in the thermal properties of the aluminum housing and the iron differential carrier the bearings have been mounted with their apices directed toward each other. However, even if the antifriction bearings are facing inward, the axial expansion difference tightens the bearings while the diameter effects are the same, canceling out the opposite effects. In order to set or position the bearings, the bearings should operate in a condition of preload, which is characterized by an absence of clearances, both axial and radial, in the bearings. However, it has proven very difficult to set or assemble these bearings when their apices are orientated inwardly due to the required press fit on the differential case. It would be advantageous to compensate for thermal expansion between an aluminum housing and an iron differential carrier and to be able to set the bearings.